Experiment on Suppression of Local Scour around Outer-Banks in Curved-Rivers by a Series of Spur Dykes

Abstract

A circular water-channel experiment was carried out to study suppression of the local scour around outer-banks in curved-rivers through the use of a series of simple rectangular spur dykes, under the condition of ‘major bed-load and minor suspended-load’. Bed variations were intensively measured around the spur dykes in the wide range of their aspect ratio Ar, defined by the super dyke interval / spur dyke length. In the range of Ar≦1, the spur dykes negatively worked and made a large scour hole in their neighboring region. On the other hand, the scour area decreased due to their effective operation in the range of Ar≧3. In particular, at Ar = 5, it would be less than a half of that in the absence of spur dykes. In conclusion, it has been verified that a series of spur dykes with the suitable values of Ar have the potential to protect outer-banks in curved-rivers.